What it returns

Field	Meaning
days	Lookback window in days, counted back from now. Ignored when `start` is given.
start	Start of the range, ISO-8601 (e.g. '2026-08-01'). Overrides `days`.
end	End of the range, ISO-8601. Defaults to now.

Parameters

Name	Type	Description
`days`	`integer`	Lookback window in days, counted back from now. Ignored when `start` is given.
`start`	`string`	Start of the range, ISO-8601 (e.g. '2026-08-01'). Overrides `days`.
`end`	`string`	End of the range, ISO-8601. Defaults to now.

Pass either days or an explicit start/end pair. start wins if both are given.

Output

A markdown table rather than JSON — roughly a third of the tokens, and models reason over rows more reliably than nested objects.

Notes and gotchas

Requires a connected Withings account. Connect it from your dashboard — no developer account needed.
Read-only: this tool cannot change anything in your account.

Call it directly

The endpoint is plain JSON-RPC, so you can test without any client:

curl

curl -s https://fitnesspeak.app/mcp \
  -H "Authorization: Bearer fp_live_YOUR_KEY_HERE" \
  -H "Content-Type: application/json" \
  -d '{
       "jsonrpc": "2.0",
       "id": 1,
       "method": "tools/call",
       "params": {
         "name": "withings_weight",
         "arguments": {
           "days": 7
         }
       }
     }'

Tool description the model sees

Body weight and composition from a Withings smart scale: weight, body-fat percentage, fat mass, muscle mass, bone mass, water and visceral fat, plus the change across the range. Call this when the user asks what they weigh, whether their weight is going up or down, or about body fat, muscle or body composition. For weights the user typed into a training log instead, use hevy_body_measurements.

Descriptions say when to call a tool, not just what it does — that trigger wording is what models actually route on.

`withings_weight`